/*
 * Phys2D - a 2D physics engine based on the work of Erin Catto.
 * 
 * This source is provided under the terms of the BSD License.
 * 
 * Copyright (c) 2006, Phys2D
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or 
 * without modification, are permitted provided that the following 
 * conditions are met:
 * 
 *  * Redistributions of source code must retain the above 
 *    copyright notice, this list of conditions and the 
 *    following disclaimer.
 *  * Redistributions in binary form must reproduce the above 
 *    copyright notice, this list of conditions and the following 
 *    disclaimer in the documentation and/or other materials provided 
 *    with the distribution.
 *  * Neither the name of the Phys2D/New Dawn Software nor the names of 
 *    its contributors may be used to endorse or promote products 
 *    derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, 
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS 
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, 
 * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR 
 * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 
 * OF SUCH DAMAGE.
 */
package net.phys2d.raw.collide;

import net.phys2d.math.MathUtil;
import net.phys2d.math.Vector2f;
import net.phys2d.raw.Body;
import net.phys2d.raw.Contact;

/**
 * A collider wrapper that swaps the collision result of the collider. This is
 * very useful to get rid of code duplication for colliders like
 * CircleBoxCollider and BoxCircleCollider.
 * 
 * @author Gideon Smeding
 * 
 */
public class SwapCollider implements Collider {

	/** The wrapped collider of which the result will be swapped */
	private Collider collider;

	/**
	 * Create a collider that swaps the result of the wrapped collider.
	 * 
	 * @param collider
	 *            The collider of which to swap the result
	 */
	public SwapCollider(Collider collider) {
		this.collider = collider;
	}

	/**
	 * @see net.phys2d.raw.collide.Collider#collide(net.phys2d.raw.Contact[],
	 *      net.phys2d.raw.Body, net.phys2d.raw.Body)
	 */
	public int collide(Contact[] contacts, Body bodyA, Body bodyB) {
		int count = collider.collide(contacts, bodyB, bodyA);

		// reverse the collision results by inverting normals
		for (int i = 0; i < count; i++) {
			Vector2f vec = MathUtil.scale(contacts[i].getNormal(), -1);
			contacts[i].setNormal(vec);
		}

		return count;
	}

}
